The present exemplary embodiment relates to radiopharmaceuticals. It finds particular application in conjunction with a dose calibrator or radioisotope calibrator, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
A dose calibrator (radioisotope calibrator) is a device used in nuclear medicine that measures the total energy of a specific radionuclide in units of Curies (Ci), millicuries (mCi), or microcuries (μCi). It includes a hollow, lead-shielded cylinder, into which radionuclides are lowered for measurement. Such devices can be programmed for specific radioisotopes, or adjusted for isotopes not preprogrammed. A dose calibrator is commonly used to obtain measurements of the total radioactivity of isotopes prior to administration to patients undergoing nuclear medicine diagnostic imaging procedures or radioisotope therapy procedures. Regulatory authorities specify when a radioisotope dose calibrator will be used and the timing of required quality control checks (constancy, accuracy, linearity, and geometrical dependence).
Currently, a dose calibration source standard is used for calibration of the dose calibrator. The calibration source includes a cylindrical vial comprising a predetermined amount of the radionuclide to be calibrated, together with a decay calendar, which allows a user to determine the amount of radionuclide present in the source at the time of testing. The current dose calibration source standards are designed to closely approximate the geometry of unit dose radiopharmaceuticals dispensed in vials by radiopharmacies (specifically, a Tc-99m generator elution vial, of 30 cc maximum volume) and may therefore only partially meet the standards implied in CEI-IEC 61145 “Calibration and Usage of Ionization Chamber Systems for Assay of Radionuclides;” CEI-IEC 1303 “Medical Electrical Equipment—Radionuclide Calibrators—Particular Method of Describing Performance;” ANSI N42.13-1986 “Calibration and Usage of ‘Dose Calibrator’ Ionization Chambers for the Assay of Radionuclides;” and 10 CFR 35.50 “Possession, Use, Calibration, and Check of Dose Calibrators.”
Nuclear medicine practitioners generally administer radiopharmaceuticals using a syringe. The practitioner places the syringe containing the radiopharmaceutical into the pre-calibrated dose calibrator to assay its content. The syringe has a different body shape from that of the calibration vials used as calibration standards and, due to the shape of the syringe and configuration of the dose calibrator, is positioned in the dose calibrator with the syringe body in a different location from the vial.